Lubricating oils containing a zinc dithiophosphate and nickel mahogany sulfonate



"TI-IIOBHQSI -HATE JAND NICKEL MAHOGANY rSULEONATE Guy Verley, Harvey, 111;, flssigno'r toISinclairRefining 'GompanyglNew Yrk,iN.Y., a corporationof Maine N0 Drawing. Application May 11, 1956 Serial- No. 584;182

This invention relatestomineral oil compositions and more particularly to .improved lubricating oils containing azinc dithiophosphate together with nickelmahogany sulfonate and preferably having other .additives such as detergents and anti-wear agents.

With .theadvent of .higher compression internalcombustion engines and increases in horsepower, much difficulty has been experiencedin formulating a suitable lubricating oil composition .capable .of operating under severe conditions to protect effectively metal surfaces which come in contact with the oil. In an effort to overcome this problem, a wide variety-of additive agents such as detergents, anti-oxidants, anti-wear agents, E. P. agents and the like have been proposed for the improvement of lubricating oils. Generally, each additive agent is employed to impart 'aparticularcharacteristic to the .base oil-so :as :to afford a =finished lubricating composition whichsis oxidation resistant, stableandnon-corrosive to hearing ;metals, .:and which .eifectively reduces varnish and sludge forming tendencies andminimizes :frictional and corrosive Wear.

"Unfortunately, however, while many of the proposed additive agents improve mineral lubricating oils, quite frequently these lubricating .oil compositions have not proved to be entirely satisfactory for commercial use since apparently an additive .agent which imparts a heneficialeffect may impart unpredictable and undesirable wear of a given engine ,part. For example, .a small amount of zinc dithiophosphate displayssatisfactory oxidation and bearing corrosion inhibiting properties in a mineral lubricating oil. This additive is particularly active in reducing the corrosion of copper-lead bearings subjected to severe operating conditions of temperature and.pressure. However, a lubricating oil containing a zinc dithiophosphate and a detergent type agent, such as, for example, basic barium mahogany sulfonate, ;was found to allow excessive wear of partslsuch as wrist pins, valve lifters and rocker arm shaftsinrecentrmodels of valve-inhead engines. Elimination of the zinc dithiophosphate reduced'wrist pin 'and rocker arm shaft wear but, of course, the resulting composition was subject to oxidative deterioration and the bad effects derived therefrom. The subsequent addition of an anti-wear agentgi. e. sulfurized sperm oil, to the composition containingthezinc dithiopho'sphate for practical purposes eliminated'wristpin wear and reduced valve lifter-wear but didnot solve the rocker arm shaft wear-problems. In fact, the anti-wear agent increased rocker arm shaft wear of the base mineral oil. Thus, both the zinc dithiophosphate and the anti-wear agent caused excessive wear -of-the rocker arm shaft and as a result this compounded oil had undesirable properties. 'Suchhas been the case when using-many additive agents and hence -much difficultyhas been experienced in formulating an engine lubricating oil of satisfactory anti-wear and anti-oxidant properties.

In accordance with the present invention '1 have discovered that an improved-mineral oil base lubricating 2,824,063 PatentedFeb. 18',

composition canlbeprenared thy; addingtsmalr niounts oi .riielrel ahogany :sulfonate .flridfa .Zinc .dithi,ophosphate .nickel and zinc components eifectively prevent rocker arm shaft wear and, substantially reduce the severe wear \vhichoccurs at contact points in rocker arms, tappets and camshafts. fBy ,rny invention :1 have further discovered that the use of these additives will not impart new and undesirable properties with respect to allowing increased wear of adifferent engine part. The nickel sulfonates employed inlthelubricating vcomposition ofmy invention are the oil-soluble nickel salts derived .from theoil-soluble sulfonic acids produced in the treatment of petroleum hydrocarbons with a sulfonating agent such as sulfuric acid or sulfur trioxide. The preferentially oil-soluble sulfonic acids, generallyreferred to as mahogany acids, are conveniently employed as a concentrate in the oil from which they are derived and may be prepared by sulfonating a suitable petroleum distillate with-fuming sulfuric .acid to obtain approximately a 10 weight percent concentration of mahogany acids in the acid oil, or by .sulfonating with sulfur trioxide, in which case approximately a 20 percent concentration is obtained. The useful mahogany acids generally have a molecular weight of about-300 (05 00 or'higher and may be converted into the nickelsalts'hy the direct neutralization of the acid oil with abasic reacting nickel, compound such as an oxide, hydroxide or carbonate. Similarly, the nickel salts maybe obtained from othermetal salts by reaction of metathesis under conditions well known in the art for effecting reactions of this type. Thus sodiurn petroleum sulfonates may be converted into nickel sulfonates by treating an oil solution of'the sodium sulfonates with an aqueous solution of nickelous chloride. In the novel lubricating compositions of my invention, a small or minor amount of nickel sulfonate is used to provide about 0.01 to 0.2 percent by weight of nickel relative to the mineral oil in which it is incorporated.

The various zinc dithiophosphates which may be incorporated in the lubricating composition of this invention can be obtained from a wide variety of diester dithiophosphoric acids conventionally preparedby reacting a sulfide of phosphorus, suchas phosphoruspentasulfide, with an alcohol, phenol or nercaptan. The organic groups in the acid esters may be aryl, allgyl, aralkyl or cycloalkyl groups which containfrorn about 4 to 20 carbon atoms, preferably about 6 to 14, and may be further substituted in the organic portion. Suitabl e alcohols which may be-employed in preparing the acid esters include oxo-alcohols, primary and secondary alcohols such as 2-methylamyl alcohol, 4 -methylpentanol 2, "Z-methylpentanol-l, 2-ethylhexanol, di-isopropyl carbinol, cyclohexanol, butanol-l and octadecanol-l, or mixtures offlhigh and low molecular weight alcohols. Other :hydroxylcontainingmaterials which can be reacted withthe phosphorus sulfide include phenols and alkylate'd phenols such as dioctylphenol, tri-isobutylphenol and the like.

A particularly suitable zinc dithiophosphate which may be employed to advantage with the nickel sulfonate is'the zinc salt obtained from a mixed dithiophosphate prepared by reacting a technical mixture of C secondary and C primary alcohols with phosphorus pentasulfide. The zinc dithiophosphate is employed m my improved lubricating composition in an amount sufi'icientto inhibit oxidation and bearing corrosion and in mostinstances the amount used provides about 0.03 to 0.2 percent byweight 15 weight percent of combined sulfur.

of phosphorus, relative to the mineral oil in which it is incorporated.

A wide variety of compounds utilized as detergents in lubricating oils to effect engine cleanliness and antisludging properties may be employed in the compounded lubricating compositions of this invention. Among the preferred detergents are the oil-soluble metal salts of petroleum sulfonic acids which can be prepared by neutralization of mahogany sulfonic acids with an oxide or hydroxide of a metal, for instance an alkaline earth metal, such as calcium or barium oxide. Preferably, the neutralization is carried out to obtain a metal sulfonate which is alkaline and of higher metal content than the normal salt. Advantageously, if desired, the basic metal sulfonate can be carbonated by treatment with carbon dioxide at atmospheric or slightly elevated pressure until the strong basicity of the sulfonate is reduced from a pH of 14 to a pH between about 7 to 8. In the practice of this invention the preferred basic barium sulfonate 'is prepared by reacting a sulfonated mineral oil fraction with at least about 1.5 times the theoretical amount of basic barium oxide required. The basic barium sulfonate is conveniently employed as a concentrate in the oil from which it is derived.

The amount of detergent type agent added to the mineral oil base will depend upon the nature of the base stock employed and its service application, and in general ranges from about 0.5% to 10% by weight on a dry soap basis. In the preferred lubricating compositions of this invention the basic barium sulfonate is added in a sufficient amount to effect a barium content of about 0.2 to 2.0% by weight. 7

Other suitable detergent type additives which also can be used include metal soaps, metal phenates, metal alcoholates, metal alkyl phenol sulfides, metal alkyl salicylates, and the like. Thus, in addition to the preferred metal petroleum sulfonates, other detergent addition agents such as barium amyl phenol sulfide, calcium cetyl phenate, basic calcium octyl salicylates, etc. may also be employed.

My present compositions can have added an anti-wear agent, particularly to reduce wrist pin wear. The anti- Wear type agents which are preferred are the sulfurized fatty oils such as sulfurized sperm oil, sulfurized rape seed oil, sulfurized cotton seed oil and sulfurized palm oil. A particularly elfective anti-wear type agent employed is sulfurized sperm oil which contains about to For anti-wear purposes the sulfurized sperm oil is usually employed in a small or minor amount sutficient to contribute about 0.06 to 0.2% by weight of sulfur on the basis of the mineral oil of the composition. Although a sulfurized oil combats wrist pin wear, it apparently promotes rocker arm shaft wear. Surprisingly, when this additive is used in my compositions containing both the zinc dithiophosphate and the nickel mahogany sulfonate rocker arm shaft wear is still not excessive.

In addition to the above-mentioned materials employed in the lubricating composition of the present invention, other additive agents such as pour depressors, anti-foam agents and viscosity index improvers may also be employed. a

The mineral oil base stock used in the present invention is of lubricating viscosity, e. g. 35 to 225 SUS at 210 F. and may be a solvent extracted or solvent re fined oil obtained in accordance with conventional methods of treating lubricating oils. The base oil may be derived from parafiinic, naphthenic, asphaltic or mixed base crudes, and if desired, a blend of solvent treated Mid-Continent neutrals and Mid-Continent bright stock may be employed. A particularly suitable base oil used in the preparation of my compositions is a solvent treated Mid-Continent neutral having a viscosity index of about 95.

The following examples, which are not to be construed aslimiting the scope of the invention, are offered to further illustrate the method of preparing the novel lubricating compositions of the present invention.

EXAMPLE I Preparation of sulfonic acid 0z'l.A sweet West Texas gas oil fraction having a viscosity of 270 SUS at F. was treated with four 28 pounds per barrel dumps of 20% oleum. The sludge was removed after each oleum dump and the acid treated oil was freed of 50;, by air blowing to leave a solution of approximately 10% mahogany sulfonic acids in oil with an acid No. of 13.0.

EXAMPLE II Preparation of nickel sulfonate.'Twenty-eight pounds of the acid oil prepared essentially as in Example I were contacted with 283 grams of NiCO (164% of theory) and 1000 grams of water for two hours at 190 F. The mixture was then dehydrated to 290 F. and filtered through blotter paper with Hi-Flo Supercel filter aid. The product analyzed 0.815% nickel with an initial pH of 1.8. The nickel sulfonate was recontacted with 270 g. NiCO and 500 cc. water for two hours at to 180 F. The mixture was dehydrated to 300 F., and filtered with Hi-Flo Supercel filter aid through blotter paper. The product analyzed 0.992% nickel and had an initial pH of 5.8 (theoretical nickel0.68%).

EXAMPLE HI Preparation of basic barium sulf0nate.The acid oil, prepared essentially as in Example I, was neutralized by mixing it with approximately 250% theoretical barium oxide in a water solution for several hours at to 180 F followed by dehydration to 300 F. This product was filtered with Supercel to leave a basic barium sulfonate which analyzed as follows:

Percent barium 3.36 Base No. to pH 4 13.9

EXAMPLE IV Preparation of zinc dithioph0sphate.A dithiophosphoric acid was prepared by reacting a technical mixture of C secondary and C primary alcohols with phosphorus pentasulfide until esterification was complete. The acid ester was then reacted with a theoretical amount of zinc oxide at 120 to F. for about 3 hours. The mixture was taken up to 250 F. and held there for one hour under vacuum. Diluent oil was then added to make about a 60% concentrate which had a typical analysis of:

Percent zinc 5.5 Percent phosphorus 5.5 Percent sulfur 10.5

Laboratory engine test Lubricating oil blends were prepared containing each of the products prepared in Examples II, III and IV using as a reference oil an extracted Mid-Continent parafiinic type lubricating oil of SAE 10 W grade. The reference oil in each of the compositions tested contained an antifoam agent and a polymethacrylate viscosity index improver and pour depressor.

In all of the following tests a standardized 100 hour cycling procedure was carried out on a popular make 1955 V-S valve-in-head engine using a particular combination of additive agents in the reference oil. Wear of the rocker arm shaft in these 100 hour tests is measured in ten thousandths of an inch. When thesevalues are quite low a better guide is the maximum surface roughness of the loaded areas which can be measured more accurately. A rough shaft indicates excessive wear or is a forerunner of excessive wear. The following results tabulated in Table I show that both the zinc dithiophosphate and the sulfurized sperm oil contribute to rough Wear of the rocker arm shaft.

I claim:

1. A lubricating oil composition consisting essentially of a major amount of a mineral lubricating oil, an oil- TABLE I soluble nlckel petroleum mahogany sulfonatc suilicient Rocker Arm Average to provide about 0.01 to 0.2 percent by weight of nickel, Test Composition Shaft Max. Wear 1}]. a zinc dithiophosphate diester in which the ester groups X contain from about 4 to 20 carbon atoms, said dithiophosphate being oil-soluble and present in an amount to 1 rovide about 0.03 to 0.2 percent phosphorus, a small 47 Reference 011 plus zine clithiophos 70 2 p phate of Ex. IV in an amount to 10 amount of sulfurized sperm 011 sufficient to impart antigggggfig fgg ggfi ggg wear properties and a small amount of basic barium 011 12% s and basic barium petroleum mahogany sulfonate suificient to impart a ifi ffgg fgig g gfiggfgfi barium content of about 0.2 to 2.0 percent by weight. 59 p s t om 15 1 2. The composition of claim 1 wherein mineral lubri- 7Q:::::: 23533; f' ;f,i ;i;g g"B5{-{ 1J 15 0 l5 eating oil is a solvent refined Mid-Continent neutral oil.

ma oganys 011a ei n an amount 53 94% Ba mm 00111 References Cited in the file of this: patent 55 Reference 011 1 plus zinc (lithiophos- 38 3 photo of Ex. IV in an amount to UNITED STATES PATENTS 5f 2,261,047 Asseif Oct. 28, 1941 04 Referenceoil plus1.25%sulfu.rlzed 40 0 2,417,876 Lewis et al. Mar. 25, 1947 51391111011622, 2,606,872 Gasser et al. Aug. 12, 1952 1 Reference oil is a SAID-10 W base stock containing polymethacrylatc FOREIGN PATENTS VI improver and pour depressor, and an antifoam agent. 658 182 Great Britain Oct 3 1951 s a The results tabulated in Table II below show that the 696,064 Great Britain Aug 26, 1953 replacement of the sulfurized sperm oil with nickel sulfonate effectively prevents rocker arm shaft wear and substantially reduces wear or rocker arms, tappets and camshafts.

TABLE II 1 Shaft Wear, In. 1o

Test 5 N 0. Composition Shafts Rockers Tappets Cams 1 App. Finnish,

p Max. Av. Max. Av. Max. Av. Max. Av.

47 Reference oil plus zinc dlthlophosphate of O-V 70 2 2 22 14 46 7 440 Example IV in an amount to provide 093% P, 1.25% sulfurized sperm oil (12% S) and basic barium mahogany sulfonate in an amount to provide 34% Ba in total composition. 97 Reference oil plus zinc dithiophosphate of O-V 30 3 2 11 5 7 3 15 8 Example IV in an amount to provide 093% P, 1.25% sulfurized sperm oil (12% S), basic barium sulfonate in an amount to provide 04% Ba and nickel sulfonate of Example II in an amount to provide 0.03% N1 in total composition. 92 Reference oil plus zine dithiophosphate of 8-01 8 2 2 3 2 6 2 4 3 Example IV in an amount to provide 09% P, basic barium sulfonate in an amount to provide 0.92% Ba and nickel sulfonate of Example II in an amount to provide 0.10% Ni in total CODIPOSitlOIl.

1 O-coarse; V-varnish; Ssmooth; 0l-clean; B-borderline. 1 Reference oil is a. SAE 10 W base stock containing polymethacrylate VI improver and pour depressor, and an aim-foam agent. 

1. A LUBRICATING OIL COMPOSITION CONSISTING ESSENTIALLY OF A MAJOR AMOUNT OF A MINERAL LUBRICATING OIL, AN OILSOLUBLE NICKEL PETROLEUM MAHOGANY SULFONATE SUFFICIENT TO PROVIDE ABOUT 0.01 TO 0.2 PERCENT BY WEIGHT OF NICKEL, A ZINC DITHIOPHOSPHATE DIESTER IN WHICH THE ESTER GROUPS CONTAIN FROM ABOUT 4 TO 20 CARBON ATOMS, SAID DITHIOPHOSPHATE BEING OIL-SOLUBLE AND PRRESENT IN AMOUNT TO PROVIDE ABOUT 0.03 TO 0.2 PERCENT PHOSPHORUS, A SMALL AMOUNT OF SULFURIZED SPERM OIL SUFFICIENT TO IMPART ANTIWEAR PROPERTIES AND A SMALL AMOUNT OF BASIC BARIUM PETROLEUM MAHOGANY SULFNOATE SUFFICIENT TO IMPART A BARIUM CONTENT OF ABOUT 0.2 TO 2.0 PERCENT BY WEIGHT. 